The present invention relates to a sound absorbing or noise reduction device for a fuel tank attached inside the fuel tank to alleviate and absorb the sound of liquid accompanied by waving of fuel and so on.
This kind of sound absorbing device, for example, is shown in FIG. 7(a) disclosed in Japanese Utility Model Publication (KOKOKU) No. 6-6986 (FIGS. 1–6), or in FIG. 7(b) disclosed in Japanese Patent No. 2719002 (FIGS. 1–12). In the noise reduction structure in FIG. 7(a), multiple plane meshes or screens 51 are used and rib-shaped protrusions 51a are laid between the screens 51 and stacked in layers at regular intervals. The mesh member 50 in the form of layer is disposed along the inner wall of a fuel tank 40 (a tank in FIG. 7(a) is a horizontal cross section), and attached through a bracket etc. not shown in the figure. Tn the operating, when the liquid or fuel of the tank 40 is moved by vibration, the fluctuation passes the mesh or screen of the mesh member 50, and is dispersed, or alleviated and absorbed in the process of passing through the screens 51, so that the kinetic energy of the fluctuation is attenuated to prevent the sound of liquid.
On the other hand, in the noise reduction structure in FIG. 7(b), a spongy baffle portion 56 is firmly fixed to a part of a bracket 55 attached inside the fuel tank 40. In the baffle portion 56, a molten resin material is slenderly extruded to the corresponding part of the bracket 55 from many exclusive nozzles as a resin rod 57; is intertwined or entangled as a cotton-waste-shape as shown on the right side of FIG. 7(b); and stacked at a predetermined size. Numeral 58 is a hook for fitting a holding plate 59 to the fixed bracket 55 on the tank side. In this operation, when the liquid fuel of the tank 40 is undulated or moved by vibration, the fluctuation is dispersed or alleviated and absorbed in the process of passing many small spaces or maze-like intervals of the baffle portion 56.
The above-mentioned conventional structure is yet unsatisfactory in terms of the following point. Namely, in the structure of Japanese Publication 6-6986, the mesh member 50 is flat and stacked in layers, and has to be attached to many places, i.e. up-and-down and right-and left portions, along the inner wall of the tank, so that the steps for attaching to the fuel tank 40 are increased. Also, if the fuel tank 40 is divided into up and down sections as shown in FIG. 7(b), the noise reduction effect may be restricted because the mesh member 50 cannot be attached to one of the up-and-down tank half members 41, 42.
In the structure of Japanese Patent No. 2719002, an expensive and exclusive equipment for forming the spongy baffle portion 56 is required. Since the baffle portion 56 is welded to the bracket 55 as the resin material is pushed out of the exclusive nozzle, the molding operation becomes complicated in order to form the stably and firmly fixed state. Since the baffle portion 56 has to be produced according to the type (size and shape) of the fuel tank 40, it lacks versatility.
The present invention has been made in order to solve the above problems and to provide a sound absorbing device for a fuel tank to be able to be mass-produced regardless of the type of the fuel tank at a lower cost.
Another object of the present invention is to provide a versatile sound absorbing device for a fuel tank having excellent quality for assembly in addition to the noise reduction.
Further objects and advantages of the invention will be apparent from the following description of the invention.